Content

This PR adds the necessary code to add a similarity mask to the exposure compensator of the stitching pipeline.

You can configure a similarity_threshold which defines a threshold on the relative error between the pixels of two images. If the error is above the threshold, it is ignored when calculating the exposure compensation. This allows the removal of ghosting artifacts due to exposure compensation when part of the images are different (for instance a moving car which would only be present on a single picture)

Note that by default the behavior is unchanged.

Example

The top 2 images are the source images. The bottom left one used a block, per channel exposure compensation. The bottom right used the same, with a similarity threshold of 0.1.

Despite the seam finder and blender doing their job perfectly, the red artifact persists due to the exposure compensator.

The red rectangle has obviously been added artificially but that kind of artifact can exist naturally (example of a moving car above).

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake
  -> The feature is not documented, but neither are the other features are the exposure compensators. They belong to the detail namespace, I guess this is why ?